[Neuropathology of mild cognitive impairment Alzheimer's disease]

The pathological study of mild cognitive impairment (MCI) was very few. Consecutive 1,628 autopsy cases from the Brain Bank for Aging Research (BBAR) with the mean age of 80.7 years were employed for this study. All the cases were studied with the BBAR protocol (www.mci.gr.jp/BrainBank/) and clasasified into Braak's seven neuforibrillary tangle (NFT) stages (0-VII) and four senile plaque (SP) stages (0-C). CDR from the most recent 545 cases were independently evaluated by three neurologists in two different occasions. Among the 1,628 cases, 10.1% fulfilled morphological requirement of Alzheimer disease, consisting of NFT stage equal to or more than IV and SP stage equal to or more than C. Postmortem assessment of CDR was possible for 486 cases amoug 545 cases with frozem half brain and 57 cases were classified into CDR 0.5. CDR 0.5 group was clinicopathologically classified into 33 cases with degenerative changes, nine cases with vascular changes and four cases with combined degenerative and vascular changes. Only 6 among the 57 cases presented pure AD pathology. These data indicate that the pathological background of MCI is not always Alzheimer disease and combined pathology with AD as well as non-AD pathology should be carefully ruled out. For this purpose, ADNI (Alzheimer Disease Neuroimage Initiative) approach could be useful to identify MCI stage of AD.